I currently have a Holley Terminator EFI installed on my Buick 455 engine. I can easily program it to hold whatever idle speed I so desire....what should I set it for LOL! It seems to be doing pretty well set at 950 rpm. Should I go lower, higher? opinions please! Scroll to about 3/4 way through this video to hear it idle. I attached pics of some of the cam specs I have as well. I have a feeling the cam was changed out but I'm not sure yet. [video=youtube;OqGw-2C5iRI]https://www.youtube.com/watch?v=OqGw-2C5iRI[/video]
I would think you would get it as low as possible while still maintaining adequate oil pressure and not creeping in drive (auto trans) and not stalling with all accessories on and pulling a healthy vacuum.
X2, plus a 200/250 rpm drop from in/out of gear is about perfect. If you cant achieve that, your convertor is too tight, or there are timing or idle fuel issues.
Keeping the upper valvetrain lubed properly would make me error on the high side of a needed idle rpm. If all you need is 750 rpm to keep the motor idling with all the lights and AC on, then go for 800 or so, especially if it will keep your hot oil pressure at 20 to 25 lbs!
That's the old SP2 Lunati cam iirc, with 44° of overlap it's going to need a little bit of rpm, depending on the LSA it may need 1k rpm. I always set idle where I get the cleanest throttle tip in , the EFI may can get it lower , but I like a faster idle cars with healthy cams idled down low sound like tractors imo
I greatly appreciate your replies. I've been messing around with it a bit and I can go as low as 500 RPM in gear but I don't think that is an ideal set-point. I've settled for about 750 in gear and all is well! Next question. Carburetor - 455 engines - what RPM would one expect to see when the engine is cold and the choke is activated? Basically, I program all the parameters into the EFI...so I've been using your advice to get a base point and then tinkering around a bit to get it dialed in...right now, cold start (20-60 degrees F) I have it set to idle at 1100. This keeps the car running but it takes some time to get the engine warmed up. What do you guys think?
I wouldn't tie myself into what a Q-jet would fast idle at. My guess is around 1400 RPM. I would experiment and set it as low as possible and still be able to throw it in gear cold and drive.
Very good point. I suppose the EFI will do what it is capable of doing and I should tune it accordingly...I was just curious as to what a Q-jet would do. Thanks for the advice!
Keep in mind that no matter what the factory specified for fast idle rpm, what actually mattered was the RPM of the cold engine on the SECOND highest step of the fast idle cam. 1. A cold engine idles slower than a hot engine, given the same throttle opening. Cold oil is harder to pump, fuel distribution is not as good, etc. 2. The only time the engine is running on the highest step of the fast idle cam is during the first few seconds after the engine has been started. Once the engine starts, you release the key from the "Start" position to the "Run" position, and almost immediately tap the gas pedal which allows the fast idle cam to rotate to the second-highest step. Total running time on the highest step is maybe five seconds. Often less. 3. Due to piss-poor mixture distribution when cold, and the general tendency to lean operation for the sake of emissions control, the factory sometimes ran the fast idle excessively high to compensate for poor fueling when cold. Fixing the mixture can permit lower fast-idle speeds. Agreed. If it doesn't stall or run rough cold, but turning it 50 or 100 rpm slower does cause stalling/hesitation/roughness when cold, you're set
